Electronic and mechanical pressure-sensing altimeters are well-known. However, these devices all suffer from calibration problems when used in a mobile context.
Ambient air pressure changes with altitude and this phenomenon is the basis of the operation of pressure-sensing altimeters. However, this causes calibration problems for barometers which are mobile.
Air pressure changes by about 1 mbar per 10 m change in altitude. Air pressure changes of a few mbars per hour can also occur as a result of the movement of weather fronts. Consequently, there is a problem in distinguishing between pressure changes caused by changes in altitude and those caused by weather conditions.
In aviation applications, altimeters are calibrated from time to time by the aircrew using local mean sea-level pressure values received from air traffic control. However, there is no similar infrastructure for providing reference pressure values for personal devices.